title: Long-term exposure to repetitive hyperbaric oxygen results in cumulative oxidative stress in rat lung tissue.
abstract: BACKGROUND
  Despite its known benefits, hyperbaric oxygen (HBO) is also reported to enhance the production of reactive oxygen species and can cause oxidative stress in several tissues. Previous studies had shown that HBO-induced oxidative stress is directly proportional to both its exposure pressure and duration. Nevertheless, these studies were usually performed with single-session HBO exposure but its clinical use commonly depends on long-term exposure periods.
  
  
  OBJECTIVE
  To clarify the oxidative effect of long-term repetitive HBO in the lung tissue of rats.
  
  
  METHODS
  Male Sprague-Dawley rats were divided into six study groups exposed to consecutive HBO sessions (2.8 atm/90  min) for 5, 10, 15, 20, 30, and 40 days. Animals were sacrificed 24  h after the last HBO session. An additional control group was set to obtain normal data. Lung malondialdehyde (MDA) and carbonylated protein (PCC) levels were determined as measures of oxidative stress along with the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase.
  
  
  RESULTS
  None of the measured parameters showed any changes among the groups exposed to 5-15 HBO sessions. However, MDA, PCC, and SOD were found to be significantly increased in the 20 to 40 session groups.
  
  
  CONCLUSIONS
  These results indicate that repetitive treatment with HBO may cause oxidative stress in critical tissues including the lung. Although HBO-mediated free radicals are accepted to be responsible for the benefits of this therapeutic modality, especially in cases with prolonged exposure, possible injurious effects of supranormal values of bio-oxidative products need to be considered.
authors.affiliation: Gulhane Military Medical Academy, Department of Undersea and Hyperbaric Medicine, Ankara, Turkey.
authors.forename: Kemal
authors.initials: K
authors.lastname: Simsek
authors.forename: Hakan
authors.initials: H
authors.lastname: Ay
authors.forename: Turgut
authors.initials: T
authors.lastname: Topal
authors.forename: Mehmet
authors.initials: M
authors.lastname: Ozler
authors.forename: Bulent
authors.initials: B
authors.lastname: Uysal
authors.forename: Ergun
authors.initials: E
authors.lastname: Ucar
authors.forename: Cengiz H
authors.initials: CH
authors.lastname: Acikel
authors.forename: Ozgur
authors.initials: O
authors.lastname: Yesilyurt
authors.forename: Ahmet
authors.initials: A
authors.lastname: Korkmaz
authors.forename: Sukru
authors.initials: S
authors.lastname: Oter
authors.forename: Senol
authors.initials: S
authors.lastname: Yildiz
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006931:Hyperbaric Oxygenation / Q000009:adverse effects*; D015227:Lipid Peroxidation; D008168:Lung / Q000378:metabolism*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D018384:Oxidative Stress; D050050:Protein Carbonylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
chemical_list: D015415:Biomarkers; D008315:Malondialdehyde; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase